Hepatitis A virus (HAV), a picornavirus, is the causative agent of an acute hepatic disease; although it is possible to grow HAV in culture and the genome has been molecularly cloned, the general biology of this virus is not well understood. Very little is known about the first step in the life cycle of HAV that is binding to a cell surface receptor which triggers infection. Interaction of HAV with its cellular receptor could be responsible for many characteristics of HAV such as restricted growth in primate cells and hepatovirulence. Therefore, study of the interaction of HAV with its cellular receptor will help to understand the mechanisms involved in the pathogenicity of this virus and specific receptor antagonists could be useful therapeutic agents. The goal of this project is to study whether presence of specific cell surface receptors are responsible for the restricted growth of HAV and to characterize and molecularly clone cellular receptors for HAV. In order to do so, we are trying to identify nonprimate cell lines capable of supporting HAV replication upon transfection of genomic RNA; cell lines are being transfected with genomic RNA and replication of HAV is being monitored by slot blot hybridization to 32P-labeled cDNA probes. Cell lines that support HAV replication upon transfection will be further analyzed. We are also raising monoclonal antibodies against cell surface molecules and analyzing whether such antibodies could protect susceptible cells against HAV infection. Once we obtained such a protective MoAb, we will be able to characterize cell surface molecules that could act as cellular receptors for HAV and molecularly clone them.